In a number of technical areas—such as the provision of touch screens—there is a need for sensing a position of an object. A position sensor should determine position accurately and reliably, whilst ideally being simple, efficient and inexpensive. This can pose considerable difficulty where it is necessary to determine a position of an object of unknown or variable width, i.e. whose size cannot be accurately predetermined. As one illustrative example, it may be desired to sense a position of an arbitrary human finger. This is problematic as each finger of a human hand is of a different width, and finger width varies substantially from person to person.